Bank 2 cat efficiency on Audi V6/V8 — typically upstream misfire damage, lazy rear O2 or coolant ingestion on 3.0T/4.2 FSI.
Audi P0430 — Bank 2 cat efficiency on Audi V6/V8 — typically upstream misfire damage, lazy rear O2 or coolant ingestion on 3.0T/4.2 FSI. Typical UK independent garage cost: £260–£2800.
What actually causes P0430 on a Audi
Audi V engines run two cats and the bank-2 (passenger side, RHD) is buried — labour cost dominates. P0430 on 3.0T is often a cracked passenger-side exhaust manifold or a lazy O2 sensor; on 4.2 FSI it's carbon and oil-burn from worn valve stem seals. Always rule out the failing plastic thermostat housing on 3.0T — coolant in the cat is death.
Audi engines that log P0430
- 3.0T supercharged (S4/S5/Q5)
- 2.7T BiTurbo (A6/A4/allroad)
- 4.2 FSI V8 (RS4/RS5/S5)
- 3.0 TDI BiTDI (A7/Q7)
How we diagnose P0430 on a Audi
- Identify Bank 2 correctly on Audi V-engines (cyl 4-6, passenger side RHD)
- Inspect exhaust manifold for hairline cracks — common on 3.0T
- Test rear O2 sensor — slow switching = lazy cat
- Check coolant level history for failed thermostat housing — coolant ingestion kills cats
- Compression test if cylinder misfires logged alongside
The common misdiagnosis to avoid
Indie quotes for both cats when only one is faulty — insist on per-bank diagnosis. Aftermarket cats on 4.2 FSI fail emission re-tests; OEM only.
Audi P0430 repair cost in the UK
Expect £260–£2800 including parts and labour at an independent garage. Main-dealer quotes on Audi are usually higher for the same job, and the spread exists because the cheap cause and the expensive cause throw the same code — pay for the diagnosis before you pay for parts.
Bob's workshop tip
Audi V-engine P0430 always check the thermostat housing first on 3.0T — a £180 housing job avoids a £2k cat replacement six months later.
Codes usually seen alongside P0430 on Audi
- P0420
- P2096
- P0011
- P0014
Symptoms drivers report with P0430
- MIL comes on after a motorway run then stays lit — no drivability change
- Slight sulphur/rotten-egg smell on hard acceleration
- MPG drop of 1–3 mpg you wouldn't notice unless you track it
- Fails emissions/lambda snapshot at MOT despite passing tailpipe CO
- Bank 2 short-term fuel trim slightly richer than bank 1 at cruise
Repairs that clear P0430
- Same diagnostic as P0420 but bank 2 side
- Replace bank 2 rear lambda first as trial
- Confirm with lambda graphing before cat replacement
For the generic, all-makes explanation of this code — meaning, every known cause and UK cost bands — see our P0430 guide.